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Effects of Nitrogen Fertilization on Polyphenol Content and Oxidase Activities in Tobacco Seedlings¹

The effects of three levels of N fertilization on polyphenol content and polyphenoloxidase and peroxidase activities in the juvenile plants of hurley and dark tobaccos, Nicotiana tabacum L. were studied in solution culture. Large amounts of polyphenols were accumulated in the leaf; smaller amounts accumulated in the root. Chlorogenic acid and two isomers were the predominant fractions of polyphenols in the leaf, but the isomer neochlorogenic acid was absent in the root. Roots contained high concentrations of scopolin and scopoletin. The latter was not detected in seedling leaves. The amount and kind of N fertilizer greatly influenced the accumulation of polyphenols. Polyphenols were lowest on medium N, whereas they accumulated in large concentrations on both high and low N solutions. As a result, quantitative difference between the high and low polyphenol strains became less significant. Plants grown in high nitrate N solution contained more polyphenols than those fed with high ammonium nutrition. Polyphenoloxidase and peroxidase activities were higher in root than in leaf extracts and in plants cultured under medium N rate than in either extreme N environment. However, in high ammonium N fertilization the activity of both oxidases increased in the leaf but polyphenoloxidase decreased in the root. The results suggest that a medium rate of N fertilization increases oxidase in roots, polyphenoloxidase in particular, accompanied by a decrease of soluble polyphenol content in leaves, and produces a maximal phenotypic contrast for leaf polyphenol concentration among tobacco strains.

Key Words: Chlorogenic acid • Scopolin • Scopoletin • Polyphenoloxidase • Peroxidase

² Assistant Professor, Research Specialist, and graduate Student (former laboratory technician), respectively.

Received for publication November 1, 1968.